Nasdaq chief Robert Greifeld said Tuesday he was worried about a US trade war with China but expects President-elect Donald Trump to adopt a pragmatic approach once he takes office.

"I do worry" about a trade war with China, "but we're mutually dependent," Greifeld said in a discussion at the Council on Foreign Relations three weeks after Trump's shock election victory.

However, he said he expects "cooler heads" to permit US technology companies to continue to sell in China.

Trump campaigned aggressively against free trade agreements and vowed to push for concessions from China, Mexico and other key partners, although he has appeared to soften his stance on that and other issues since the election.

Greifeld said he expects Trump will seek a "refinement" of existing deals such as the North American Free Trade Agreement, rather than a full-scale replacement.

"Clearly he got elected because people were not positively affected by NAFTA."

But he suggested free trade was inexorable given the proliferation of digital currencies and other technologies that expand naturally beyond national borders.

"The pace of change is going to hit in the next five years," he said.

Greifeld spent election day in Portugal and watched results into the wee hours. Nasdaq that night was distressed as Trump's win initially sent stocks spiraling, but they quickly pivoted to move upward, leading to in numerous records closing levels following the vote.

The about-face in stocks showed "the markets don't always listen to the media," he said. "Forget the other issues, you just elected a very pro-business president."

Greifeld said he was concerned about European elections heading into 2017, but did not have any designs on what would happen.

"Obviously globalization has not helped everyone in a uniform way and in a democracy people are allowed to vote."